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Fri, 6 Nov 2026 18:24:00 -0600 From: "Nikhil P. Rao" Subject: [PATCH net 0/2] ionic: fix Tx stalls on TSO skbs larger than the Tx ring Date: Sat, 7 Nov 2026 00:23:42 +0000 Message-ID: <20261107-b4-ionic-tso-max-segs-v1-0-67c248a5b681@amd.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIAI5v7moC/yWM0QqDMBAEf0Xu2YNEtGJ/pfhg4mqv0FhyUQTx3 03bx1l25iBFFCjdi4MiNlFZQgZbFuSfQ5jBMmamylQ3a03LruZ8Ec9JF34POytmZdO0bkTnJ9Q dZfcTMcn+6z4oIFH/H3V1L/j0LdJ5XvBAMwB+AAAA X-Change-ID: 20261107-b4-ionic-tso-max-segs-057bde9cfe49 To: Brett Creeley , Andrew Lunn , "David S. Miller" , "Eric Dumazet" , Jakub Kicinski , Paolo Abeni CC: , , Breno Leitao , Eric Joyner , Abhijit Gangurde , "Nikhil P. 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A TSO skb with more segments than the Tx ring holds can never be posted: the queue stops with the ring empty, nothing wakes it, and the netdev watchdog fires again after every reset. A 64 KB TSO skb needs more than 1023 segments, the limit of the default 1024-entry ring, once the MSS is below 64 bytes. Patch 1 rejects Tx ring sizes below 64. The completion path wakes a stopped Tx queue only once 44 descriptors are free, so a smaller ring can stall on its own, and patch 2 would otherwise let such a ring lower gso_max_segs to a uselessly small value. Patch 2 advertises tso_max_segs from the Tx ring size and keeps it in step with ethtool -G, so the stack sizes TSO skbs to fit the ring and segments larger ones in software. Tested with the in-tree driver in a VM with the PF passed through: GSO frames with a virtio-net header and about 1500 segments, injected through a tap redirected to the ionic netdev with tc mirred, stalled the Tx queue before the series and are sent without a stall after it; tso_max_segs follows ethtool -G with the interface up and down, and a Tx ring of 32 is rejected. This series was developed with the help of an LLM-based coding assistant (Claude). --- Nikhil P. Rao (2): ionic: reject Tx ring sizes below the minimum ionic: limit TSO segments to the Tx ring size drivers/net/ethernet/pensando/ionic/ionic_ethtool.c | 19 ++++++++++++++++--- drivers/net/ethernet/pensando/ionic/ionic_lif.c | 10 +++++++--- drivers/net/ethernet/pensando/ionic/ionic_lif.h | 10 ++++++++++ 3 files changed, 33 insertions(+), 6 deletions(-) --- base-commit: a36b9e205cb3c452ab96cc783e63465d466fe615 change-id: 20261107-b4-ionic-tso-max-segs-057bde9cfe49 Best regards, -- Nikhil P. Rao